Process for sulfonating detergent alkylates



United States Patent Ofiice 2,723,990 Patented Nov. 15, 1955 PROCESS FOR SULFONATING DETERGENT ALKYLATES No Drawing. Application December 24, 1949, Serial No. 135,046

Claims. (Cl. 260--505) This invention relates to improvements in the manufacture of detergents, and more particularly to a process for the direct sulfonation of alkyl substituted mononuclear aromatic compounds with gaseous sulfur trioxide as the sulfonating agent. i

In recent years, the higher alkyl aromaticsulfonates have received wide acceptance as synthetic detergents for many purposes. Among such detergents are certain higher alkyl substituted mononuclear aromatic monosulfonates in which the alkyl groups are predominantly in the range containing from 8 to 20 carbon atoms; many of the more useful alkylates predominating in compounds containing 12 to 14 carbon atoms in the alkyl side chain. The alkyl groups in such compounds are usually mixtures, the compositions of which depend to a great extent on their source, such as, for example, petroleum distillate fractions, mixed olefins, etc., so that the alkyl aromatic sulfonates derived from such sources and having similar boiling ranges, while predominating in alkyl groups having the same or similar numbers of carbon atoms, may contain small quantities of lower and higher alkyl groups. Thus, the so-called dodecyl benzenes and dodecyl toluenes dried products may contain about 40% of the active alkyl aryl sodium sulfonate detergent material and about 60% of sodium sulfate.

It is known that for some purposes, the presence of substantial quantities of sodium sulfate and other inorganic salts exerts a beneficial effect on the detergent characteristics of the alkyl aryl sodium sulfonate product. However, for other purposes, high percentages of sodium sulfate are disadvantageous, particularly in cases where additives or builders other than sulfates are desired, for example phosphates or silicates. For these purposes, it is desirable to utilize a detergent having a low percentage of sodium sulfate and the highest possible percentage of active ingredients. So-called salt-free detergents have been produced to fill this need, such saltfree products usually containing from about 10% to about 15% of sodium sulfate.

of this character usually contain minor quantities of aroit matic alkylates containing lower and higher carbon alkyl groups mainly in the range of Cu to C14 alkyl groups together with the predominating C12 alkyl aromatic compounds. The alkyl groups of these alkylates are of mixed configuration, and the products are mixtures as is well known.

The alkylated mononuclear aromatic compounds useful in our process may be prepared according to any suitable well known method, such as by the alkylation of benzene or toluene with, for example, petroleum hydrocarbons of the kerosene type boiling within the range of 185 C. and 215 C. according to theprocess described, for example, in U. S. Patent 2,267,725, or of the olefin type as described, for example, in U. S. Patent 2,439,457. Such alkylated aromatic compounds are often referred to as detergent alkylates.

It has been common practice in the past to prepare water-soluble detergents from such detergent alkylates by treating them with sulfonating agents to introduce a sulfonic acid group into the benzene ring and then to neutralize the sulfonic acid-containing products with an alkali metal hydroxide, for example sodium hydroxide, to produce the alkali metal salts of the sulfonic acids and of the unreacted sulfonating agent. i

In carrying out the sulfonation process in the past upon such detergent alkylates, it has been the practice to add large excesses, up to about 300% excess, of concentrated sulfuric acid The preparation of such salt-free materials has pre sented considerable difliculty. One method widely used is to subject the composite material to solvent extraction whereupon the active detergent materials, i. e., the alkyl aryl sodium sulfonates, are dissolved, leaving behind the inactive sodium sulfate and other inorganic salts. This process is costly since the sodium sulfate is discarded and solvent losses are usually high.

Another method used in the prior art for obtaining a salt-free product involves dilution of the: acid sulfonation mixture with water to a point where the spent sulfuric acid portion on the one hand and the organic sulfonic acids on the other, stratify This procedure is likewise unsatisfactory since it involves disposal or recovery of large quantities of dilute sulfuric acid contaminated with organic materials.

It has further been proposed to produce a salt-free product by direct reaction of S03 with the alkylate according to the illustrative equation In actual practice this process has been unsatisfactory since sulfur trioxide is so strongly reactive that it chars and decomposes the detergent alkylates when added dropwise in liquid form even when the reaction mixture is kept at a temperature as low as 60" C. Since the finished detergent, to be commercially acceptable, must, for most purposes, possess a light color, generally not darker than a tan, such char-ring is extremely objectionable as it causes darkening of the color of the finished product in addition to contributing to alkylate losses in the operation. Efforts to avoid objectionable charring in dissolving S03 in an inert solvent such as tetrachloroethane, liquid sulfur dioxide, etc.,

expensive to recover and losses are usually high. Introducing the S03 as oleum produced some improvement in reducing the proportion of inert salts, but oleums containing above about 25% free S03, often result in excessive charring of the organic charge, so that the use of more concentrated oleums is precluded since alkylates of commercially acceptable color could not readily be produced from them. This means in effect that light colored alkylates, containing only about 60% activeingredients, can be obtained through the use of oleum. Moreover, while certain sulfonation processes have been carried out in the sulfuric acid plant), is used as the sulfonating agent, we have found that when such expedient is applied to the alkylated mononuclear aromatic compounds, contemplated for use in our invention the mixture becomes so viscous as the sulfonation proceeds, that it cannot readily the use of S03 by first be carried to completion so that such method is unsatisfactory for such purposes.

A process recently proposed for preparing oil-soluble alkyl aryl sulfonates, i. e. alkyl aromatic sulfonates having more than 17 carbon atoms in the alkyl group, to obtain sulfonates having a low inorganic salt content, utilizes S03 in vapor form introduced directly into the liquid aryl alkylate. This process, however, produces considerable resulting oxidation and charring of the alkylate as evi- V denced by the presence of S02 and water among the byproducts'of the sulfonation. Since the oil-soluble sulfonates thus produced (sometimes known as mahogany soaps or brown acid soaps because of their characteristic color) are commonly utilized as lubricating oil additives, the presence ofsome carbon due to charring may not be objectionable. When such process, however, is appliedt'o alkyl benzenes and toluenes for the purpose of preparing detergent products, two major objections are observed; first, the amount of charring caused by the S03 is so objectionable as to darken the product to an extent which precludes its general merchantability as a detergent, and, secondly, such process results in such an increase in viscosity of the charge as the reaction proceeds, that agitation becomes excessively difficult, if not practically impossible by' ordinary means when the charge is only about 70% sulfonated. As a result, the S03 gas can no longer be adequately distributed throughout the reaction mixture and hence sulfonation beyond the 70% point under such conditions is virtually impossible. Such process fails to produce the desired salt-free product, and moreover is contaminated with up to about 30% of unreacted, oily alkylate. Such large quantities of unreacted oil, while possibly not objectionable in a lubricant additive, tend to complicate further processing in detergent manufacture or necessitate additional steps to effect its removal.

It is an object of the present invention to provide a process for sulfonating alkyl substituted mononuclear aromatic compounds having alkyl side chains containing predominantly from 8 to 20 carbon atoms inclusive, in a manner which results directly in a commercially saltfree alkyl aryl sodium sulfonate product.

It is a further object of the invention to provide a process for effecting the direct sulfonation of alkyl substituted mononuclear aromatic compounds having alkyl side chains containing predominantly from 8 to 20 carbon atoms inclusive, with gaseous sulfur trioxide without appreciable darkening or charring of the product.

It is a still further object of the invention to effect substantially 'complete sulfonat'ion of such alkyl aromatic compounds through the use of gaseous sulfur dioxide as the sulfonating agent.

Other objects will appear as the description. of the invention proceeds.

These and other objects are accomplished according toour invention wherein alkyl substituted mononuclear aromatic compounds having alkyl side chains containing predominantly from 8 to 20 carbon atoms inclusive, are

The detergent alkylates are commercial products known by various trade names. The commercial dodecyl benzenes and toluenes of this character usually boil within the range between about 530 F. and about 630 F.; the dodecyl benzenes usually boiling predominantly between about 550 F. and about 575 F.; the dodecyl toluenes usually boiling predominantly between about 550 F. and about 600 F.

The quantity of sulfuric acid to be added to the deter gent alkylate hydrocarbon should be large enough to insure a sufficiently fluid reaction medium during the entire course of the sulfonation reaction, such that adequate distribution of SOs-inert gas mixture is obtained to prevent charring and to obtain such distribution without unduly vigorous agitation. Since the free sulfonic acids of the alkylated benzenes and toluencs are extremely viscous, the viscosity of the reaction mass becomes progressively greater as the sulfonation reaction proceeds and nears completion. The quantity of sulfuric acid used depends'to some extent upon the nature of the particular detergent alkylate to be sulfonated and upon its viscosity development upon direct sulfonation, as well as on the kind and amount of agitation used. When vigorous agitation is provided, smaller quantities of sulfuric acid may be used than when the agitation is of lesser force. In general, it'is desirable touse as small a quantity of sulfuric acid as is consistent with fluidity and prevention of charring, when alkyl aryl sodium sulfonates'of the lowest possible sodium sulfate content are desired, since the quantity of sodium sulfate in the in substantially direct molar proportion to the quantity of sulfuric acid used, the sulfuric acid being virtually completely converted into sodium sulfate. Thus, our process provides a method for obtaining directly, without special purification of the product, any desired final sodium sulfate content in the finished product above a certain minimum of about 7% imposed by the minimum essential quantity of sulfuric acid by simply increasing the quantity of sulfuric acid added to the charge. How ever, since alkyl aryl sodium sulfonate products containing-more than about 60% active product (40% sodium sulfate) are not readily obtained by sulfonations with oleum, our process is particularly valuable in making diluted and mixed with a minor proportion of concentrated sulfuric acid andthereafter are directly sulfonated with agaseous mixture of sulfur trioxide and an inert gaseous diluent.

The detergent alkylates adapted for sulfonation according to the. processof our invention as brought out above are alkyl substituted mononuclear aromatic compounds having alkyl side chains containing predominantly from 8 to 20 carbon atoms inclusive, among which are the particularly useful alkylated benzenes and toluenes boiling within the range between about 530 F. and about 630 F.', and in which the long chain alkyl groups contain predominantly 12 carbon atoms. Thus, among the preferred alkylates are the so-called dodecyl benzenes and dodecyl toluenes. in such compounds the alkyl groups may be of mixed configuration and the products contain minor proportions of higher and lower alkyl groups mainly in the Cu to C14 range.

possible the use of quantities of sulfuric acid which will produce lower salt content products, that is, quantities of sulfuric acid betweenabout 5% and about 30% (cal-v culated as monohydrate, i. e. 100% sulfuric acid) based on the weight of the alkylate, although higher percentages may be employed if desired. We find that the use of about 10% sulfuric acid produces a product usually containing roughly about 12% of sodium sulfate,- and thus results in a product which is commercially considered salt-free. Y

The concentration of the concentrated sulfuric acid used is not particularly significant, since all water present is converted to sulfuric acid upon introduction of 803. Any appreciablewater present should be taken into account in calculating the amount of H2504 eventually present in the charge. In general, 100% sulfuric acid is satisfactory, but as indicated above, less concentrated acids may be used, in which case the quantity is regulated accordingly.

The sulfur trioxide used as the active ingredient of the gaseous sulfonating mixture may be obtained from any suitable source, as stripped from oleum, or vaporized from stabilized liquid sulfur trioxide, and mixed with air, nitrogen or other inert gas by any suitable known means, as by merging separate streams of S03 and diluent gas before introduction into the liquid reaction medium, or

by bubbling the inert gas through liquid 503, etc; or the sulfur trioxide maybe in the form of the well known converter gas from the contact sulfuric acid process,

such converter gas being usually an air-S03 mixture containing between about 8% and about 15% S03. The

5 gaseous mixture will preferably be introduced into the finished product is liquid detergent alkylate-sulfuric acid charge in such a way as to facilitate its distribution throughout the charge, for example by introduction at or near the bottom of a charge through a perforated tube, coil or other distributor, positioned for example below or near the agitation mechanism. The $03 concentration of the SOs-inert gas mixture may range up to about 80% S03 by volume without undue darkening or charring of the reaction mixture if adequate agitation is provided, quickly and thoroughly to distribute the S03 and to disperse the heat of reaction. We have also found that S03 concentrations as low as about 5% will effect virtually complete sulfonation of the charge, but at this low concentration, the presence of large volumes of inert gas results in ineflicient utilization of S03, a considerable proportion of the S03 tending to pass through the charge unreacted and hence to create a problem of corrosive exit gas disposal. Accordingly, we prefer to use SOs-inert gas mixtures containing between about 15% and about 75% S03 and we havefound that a 50% S03 concentration, i. e. about equal partsof inert gas and S03 by volume is satisfactory.

The quantity of SO: introduced should be suflicient to produce complete monosulfonation of the aromatic nucleus of the aryl alkylates. Accordingly, a quantity of S03 equal to at least about the molar equivalent of the aryl alkylate is used, and preferably a slight excess of S03, for example excess, is conveniently used.

Any suitable gaseous material which is inert to the aryl alkylates and to thesulfonation reaction is suitable as a diluent for the S03; for example, air, nitrogen, carbon dioxide or the like. it i i The temperature of the reaction mixture during introduction of S03 should be maintained at a point low enough to prevent oxidation or charring of the alkylate. In general, the temperature should not be allowed to rise above about 35 C. during the initial major portion of the S03 addition, and preferably should be maintained between about C. and about 30 C., although a rise of temperature to as high as about 50 C. during the latter stages of the addition is not unduly harmful. Since the sulfonation reaction is exothermic, external cooling is provided and the charge temperature depends largely upon the degree of cooling and the efiiciency of the agitation applied. It may be further controlled to some extent by varying the rate of addition of the S03- inert gas mixture.

In carrying out the process according to our invention, a charge of the liquid alkyl aryl hydrocarbon detergent alkylate as defined, is placed in a reaction vessel equipped with external cooling, with agitation and with means for introducing gaseous sulfur trioxide-inert gas mixture into the liquid charge, preferably at a point or position such that the gas is promptly and efliciently distributed throughout the liquid mixture to avoid local oxidation or charring of the hydrocarbon charge.

The alkyl. benzene or toluene hydrocarbon charge is cooled to a point somewhat below normalroom temperatures, for example to between about 5 C. and about 10 C., and sulfuric acid, in an amount equal to at least about 5% by weight of the hydrocarbon is intimately mixed with the charge, as by agitation, while preferably maintaining the temperature below about 25 C. Then a gaseous mixture of sulfur trioxide and an inert gas such as air or nitrogen is introduced into the charge, and distributed therethrough as by agitation, while maintaining the mixture at a temperature not higher than about 50 C., for example between about 15 C. and about 50 C. during the addition of S03. After a sufficient quantity of S03 has been introduced to produce substantially complete sulfonation of the charge, introduction is discontinued and, if desired, the mixture may be digested, with continued period sutficient to insure completion of the sulfonation reaction. The term complete sulfonation is used in the sense that virtually the entirealkyl benzene or toluene charge is monosulfonated. Thus, completeness of su'l fonation in this sense is roughly measurable in the quan tity of unreacted oil remaining in the charge. During the digestion period, external cooling may be discontinued, and the temperature of the mixture allowed to rise spontaneously, usually to about 4055 C. If desired, the reaction may be completed by heating externally to, for example, 60 C. and digesting, with agitation, an additional short period at this temperature, a half hour usually being sufficien Upon completion of the sulfonationreaction, the viscous liquidsulfonic acids of the detergent alkylates may be recovered as such, if desired. However, if detergents are to be prepared, the mixture is carefully neutralized, for example with sodium hydroxide to yield a product containing the sodium salt of the alkyl aryl sulfonic acids and an amount of sodium sulfate roughly the molar equivalent of the quantity of sulfuric acid used in the original reaction mixture. The reaction product may then be dried by suitable known means, for example by drum drying, and is then ready for use or sale.

The following examples further illustrate our invention. Parts are by weight unless otherwise indicated.

EXAMPLE 1 7 To 238 parts (1.0 mol) of an alkyl benzene, consisting predominantly of dodecyl benzenes and having the specifications listed below:

i Engler range IBP 2% F 541 5% F 546 10% F 550 50% F 567 80% F 582 90% F 594 95% F 608 98% F 625 FBP F 630 Apparent molecular weight 243 Specific gravity at 86 F .t 0.8649 Aniline point F 47 Bromine number 0.24 Saybolt viscosity-hydrocarbon at 86 F 53 Centipoise viscosity-sulfonic acid at 35 C 28 Refractive index ND (26 C.) 1.4879

agitation, for an additional Percent unsulfonated using 1.25# ratio 20% oleum ColorSaybolt maintained at 5-10 C. in a container equipped with agitator, thermometer, drying tube and dropping funnel, was added dropwise with agitation 23 parts of 96% sulfuric acid. After addition was completed, the dropping funnel was replaced by a gas inlet tube of such character and so positioned as to introduce gas into the bottom of the container in the form of. bubbles at a. point below the agitator. A mixture of about equal parts of gaseous S03 and air was then passed into the reaction mixture through the inlet tube while agitating and subjecting the mixture to external cooling. Introduction of the gas was continued for about an hour, at such a rate of addition and agitation that the temperature of the mixture was maintained at 20 C. i3. A total of 89.2 parts of S0; was introduced, of which 83.0 parts were absorbed by the reaction mixture. After completion of gas addition, stirring was continued for an additional 1 /2 hours with cooling discontinued. The temperature rose spontaneously to 40 C., after which the mixture was externally heated to 50 C., and stirred at this temperature for an additional one-half hour. The mixture was then poured onto 400 parts of ice and carefully neutralized with 30%, sodium hydroxide solution. The re.- sulting slurrywas dried and produced a light creamcolored' product which was' found to contain 3.2% unreacted alkylat'e, the remainder being sulfonated dodecyl benzene and sodium sulfate.

EXAMPLE 2 To 1240 parts (5.0 mols),of an alkyl toluenepconsisting predominantly of dodecyl toluenes, and having the specifications listed below:

' in a container equipped with agitator, thermometer, drying tube and dropping funnel were added dropwise with agitation 124 parts of 96% sulfuric acid while maintaining the temperature of the mixture between 5 C. and C. After completion of addition, the dropping funnel was replaced by a gas inlet tube of a character similar to that described in Example 1. A mixture of about equal parts of air and gaseous S03 was introduced into the bottom of the. reaction mixture through the inlet tube while stirring and externally cooling the mixture to maintain its temperature between C. and C. The gas, introduction was continued for 1% hourswhen 423 parts of. 803 had been absorbed of a total of 441 parts furnished. Then cooling was discontinued, and stirring of the mixture continued for an additional 2 hours, the temperature rising to C. The mixture was heated to 50 C. and'stirred at this temperature for an additional one-half hour. A portion of the product was poured onto ice" and carefully neutralized with 30% sodium hydroxide solution. The resulting slurry was dried on a hotplate' and analyzed. The dry product was a light cream color, and contained 5.6% unreacted oil.

EXAMPLE 3 To 238 parts of an alkyl benzene material, consisting predofninantlyof dodecyl benzenes, and having the same characteristics as the material used in Example 1, were added 24 parts-(10%) of 96% sulfuric acid dropwise with agitation as described in Example 1, while maintaining the temperature at 5+10 C. After addition was complete, a mixture of about equal parts of gaseous sulfur dioxide and air was introduced during a period of about 1% hours at 23-30 C(until 108 parts of S03 had been added, of which 100.7 parts were absorbed by the reaction'riiixture. After completion of gas addition, stirring" was continued for an additional 2 /2'hours', during which time the temperature rose spontaneously to 38' C. At the end'of this time the reaction mixture was poured onto 400 parts of ice and carefully neutralized with 30% sodium hydroxide solution. The resulting slurry was dried, and produced a tan-colored product which contained 11.9% sodium sulfate, 86.9% dodecyl benzene sodium sulfonates, and 1.2% unreacted oil.

, EXAMPLE 4 To 238 parts of an alkyl benzene material, consisting predominantly of dodecyl benzenes, and being similar .to the material used in Example 1, were added 59.5 parts (25%) of 96% sulfuric acid dropwise with agitation as described in Example 1, and while maintaining the temperature at 5 -10 C. After addition was complete, a mixture of about equal parts of gaseous sulfur trioxide and air was introduced into the liquid reaction mixture during a period of one hour, while maintaining the temperature between 15 C. and 25 C. 84.7 parts of S03 were introduced, of which 81.6 parts were absorbed. The mixture was then digested for 2 hours at 35 -55 C., neutralized and dried. The dry product was virtually white, contained about 17% sodium sulfate, 3.4% unreacted oil, and 79.6% sulfonated alkylate.

EXAMPLE 5 60 parts of a predominantly dodecyl benzene alkylate, having physical properties similar to those described in Example 1, were placed in a glass-lined kettle equipped with a 125 R. P. M. agitator and refrigeration. 6 parts of 100% sulfuric acid were added to the dodecyl benzene and thoroughly mixed therewith, while maintaining the temperature at about 9,10 C. 26 parts of sulfur trioxide vapor were introduced in admixture with about equal parts of air over a period of about 4 hours while agitating the charge. The temperature was about 9 C. at the start and was; permitted to rise gradually to a final temperature of 45 C., whereupon it was aged at this temperature forran additional two hours while continuing the agitation. The resulting product was neutralized with sodium hydroxide, the slurry was dried and produced a light tan-colored product containing 82% dodecyl benzene-sodium sulfonates, 3.7% unreacted oil content based on the sulfonates, the remainder-being inert salts primarily sodium sulfate.

EXAMPLE 6 74 parts of an 'aeid washed keryl benzene type detergent alkylate,.prepa'rcd as described in U. S. Patent 2,3 87,572, Example 1, parts 1 and 2 thereof, from a' kerosene fraction having a boiling range of about 209 C. to 250 C., and of which distilled between 209 C. and 240 C., were mixed with 7.4 parts of sulfuric acid while maintaining the temperature between 5 C. and 10 C. A mixture of equal parts of air and 503 were introduced into the mixture over a period of about 4 hours at a temperature. between 10 C. and 30 C. while agitating the mixture during which. 88.5 parts of S03 were absorbed.

. The reaction mixture was aged for an additional hour at 30 C. and neutralized with sodium hydroxide. The resulting slurrywas dried and yielded a product'with a satisfactory light tan color, containing 64% of alkyl benzene sodium sulfonates, and 4.7% of unreacted alkylate.

. EXAMPLE 7 A quantity of an alkyl benzene consisting predominantly of dodecyl benzenesand having the same specifications as the alkylate used in Example 1, amounting to 2582' parts, was mixed with 129 parts of 97% sulfuric acid (equivalent to 5% of the Weight of the alkylate) and placed in a homogenizer. into the mixture was led a stream of gases containing approximately 77% SOs vapor and 23% of dry air hyvo'lum'e, over a period of about 3 hours during which time 13.19 parts of SO; were absorbed. The temperature ranged from 8 C. atthe beginning of the addition to 43 C. at the end or the addition. Stirring was continued for an additional. hour at 50 C., whereupon the mass was neutralized and dried. It yielded a 'iight tan product containing 87% alkyl benzene sodium sulfonate, 10.8% sodium sulfate and 2.2% of oil based on the alkyl benzene sodium sulfonate content.

EXAMPLE 8 enizer. Into the charge was led over a period of 3.2 hours, a mixture of S03 vapor and air containing 91 volume percent of air and 9 volume percent of S03, during which time the temperature rangedfrom 9 C. at the beginning of the addition to about 50 C. at the end. Stirring of the charge was continued for an additional hour at 50 C. Neutralization and drying yielded a product with 1.6% oil based on the alkyl benzene sodium sulfonate content. The producthad a light tan color and contained 85.4% alkyl benzene sodium sulfonates and 13.2% sodium sulfate.

We claim:

1. In a process for the sulfonation of detergent allrylates, the steps which comprise mixing a liquid detergent alkylate consisting of alkyl substituted mononuclear aromatic compounds having alkyl side chains containing predominantly from 8 to 20 carbon atoms inclusive, with a quantity of concentrated sulfuric acid equal to at least about by weight of the detergent alkylate, thereafter introducing into and uniformly distributing throughout the liquid mixture a gaseous mixture containing at least about 5% and not more than about 80% by volume of sulfur trioxide, the remainder being an inert gas, the quantity of said gaseous mixture introduced being an amount sufiicient to eifect substantially complete monosulfonation of the nuclear radical of the alkylate, while maintaining the temperature of the mixture at not more than about 50 C. during the introduction of the gaseous mixture, and digesting the mixture until monosulfonation is substantially complete.

2. The process of claim 1, wherein the detergent alkylate is a mixture consisting predominantly of C12 alkyl benzenes.

3. The process of claim 1, wherein the detergent alkylate is a mixture consisting predominantly of C12 alkyl toluenes.

4. The process of claim 1, wherein the inert gas is air.

5. The process of claim 1, wherein the gaseous mixture contains about equal parts of sulfur trioxide and air.

6. The process of claim 1, wherein the quantity of sulfuric acid is between about 5% and about 30% by weight of the detergent alkylate.

7. The process of claim 1, wherein the quantity of sulfuric acid is equal to about by weight of the detergent alkylate and wherein the gaseous mixture contains approximately equal parts of sulfur trioxide and air.

8. In a process for the sulfonation of detergent alkylates to produce a commercially salt free product, the steps which comprise mixing a liquid detergent alkylate selected from the group consisting of long chain alkyl substituted benzenes and long chain alkyl substituted toluenes in which the long alkyl side chains contain predominantly 11 to 14 carbon atoms inclusive, with a quantity of concentrated sulfuric acid equal to between about 5% and about 10% by weight of the detergent alkylate, thereafter introducing into and uniformly distributing throughout the liquid mixture, a gaseous mixture containing approximately equal parts by volume of sulfur trioxide and air, the quantity of said gaseous mixture introduced being an amount sufiicient to effect substantially complete monosulfonation of the benzene radical of the alkylate, while maintaining the temperature of the mixture at not more than about C. during the introduction of the gaseous mixture and digesting the mixture until monosulfonation is substantially complete, neutralizing the mixture thus produced with sodium hydroxide, whereby an alkyl aryl sodium sulfonate detergent product is obtained containing not more than about 12% by weight of sodium sulfate.

9. In a process for the sulfonation of long chain alkyl mononuclear aromatic hydrocarbons, the improvement comprising contacting said hydrocarbons containing a small amount of sulfuric acid with a mixture of sulfur trioxide and an inert gas, said mixture containing at least 5% by volume of sulfur trioxide, at a temperature of about 40 C.

10. In a process for the sulfonation of a long chain alkyl mononuclear aromatic hydrocarbon, the improvement which comprises contacting said hydrocarbon, in admixture with a small amount of sulfuric acid and at a sulfonation temperature not substantially in excess of about 40 C., with a mixture of sulfur trioxide and an inert gas, the last-named mixture containing at least 5% by volume of sulfur trioxide.

References Cited in the file of this patent UNITED STATES PATENTS 1,422,654 Grob July 11, 1922 2,203,441 Oliver June 4, 1940 2,205,924 Frame June 25, 1940 2,467,176 Zimmer Apr. 12, 1949 FOREIGN PATENTS 539,281 Great Britain Sept. 3, 1941 OTHER REFERENCES General Chemical Division Bulletin, Sulfan (1947). General Chemical Division Bulletin, Reactions of S03 (1948), pgs. 2 and 12. 

1. IN A PROCESS FOR THE SULFONATION OF DETERGENT ALKYLATES, THE STEPS WHICH COMPRISE MIXING A LIQUID DETERGENT ALKYLATE CONSISTING OF ALKYL SUBSTITUTED MONONUCLEAR AROMATIC COMPOUNDS HAVING ALKYL SIDE CHAINS CONTAINING PREDOMINANTLY FROM 8 TO 20 CARBON ATOMS INCLUSIVE, WITH A QUANTITY OF CONCENTRATED SULFURIC ACID EQUAL TO AT LEAST ABOUT 5% BY WEIGHT OF THE DETERGENT ALKYLATE, THEREAFTER INTRODUCING INTO AND UNIFORMLY DISTRIBUTING THROUGHOUT THE LIQUID MIXTURE A GASEOUS MIXTURE CONTAINING AT LEAST ABOUT 5% AND NOT MORE THAN ABOUT 80% BY VOLUME OF SULFUR TRIOXIDE, THE REMAINDER BEING AN INERT GAS, THE QUANTITY OF SAID GASEOUS MIXTURE INTRODUCED BEING AN AMOUNT SUFFICIENT TO EFFECT SUBSTANTIALLY COMPLETE MONOSULFONATION OF THE NUCLEAR RADICAL OF THE ALKYLATE, WHILE MAINTAINING THE TEMPERATURE OF THE MIXTURE AT NOT MORE THAN ABOUT 50* C. DURING THE INTRODUCTION OF THE GASEOUS MIXTURE, AND DIGESTING THE MIXTURE UNTIL MONOSULFONATION IS SUBSTANTIALLY COMPLETE. 